BACKGROUND: This global systematic review assesses the prevalence of injecting drug use (IDU) and key infectious diseases (HIV, hepatitis C virus [HCV], tuberculosis and hepatitis B virus [HBV]) among people who are incarcerated.

METHODS: We conducted a systematic search of peer-reviewed (Medline, Embase, PsycINFO), internet, and grey literature databases, from January 2000 through 2nd June 2025 and engaged international experts and relevant agencies liaising with key agencies focused on incarcerated populations (WHO, UNODC, UNAIDS and EUDA). Data on study methods, size of incarcerated populations and demographic characteristics, and prevalence of IDU, HIV, HCV, HBV and tuberculosis among incarcerated populations were extracted. Meta-analyses pooled data where multiple estimates were available for a country; regional and global estimates were calculated, weighted by incarcerated population size. We present overall country, regional and global prevalence estimates for each variable examined, stratified by sex. We then estimated the ratio of IDU, HIV, HCV, HBV and tuberculosis prevalence among incarcerated populations compared to the general population.

RESULTS: Of 75,755 screened documents, 2,968 were eligible for data extraction. There are approximately 11,322,000 people aged 15-64 years incarcerated globally with their incarceration rate being 221 per 100,000 (29 per 100,000 among females and 404 per 100,000 among males). Substantial variation in rates across countries and regions were observed with the highest regional rate being in North America. Globally, we estimate that 11·9% of people who are incarcerated have ever injected drugs (1,348,000; 95%CI 1,061,500-1,687,000), 51·4 times higher than the general population. We estimate that 3·7% (95%CI 2·5-5·4) of people who are incarcerated globally are living with HIV (25.1· times higher than the general population); 11·7% (95%CI 7·7-17·1) have current HCV infection (15·6 times higher); 4·4% (95%CI 2·4-7·7) have current HBV infection (2·2 times higher) and 2·5% (95%CI 1·5-3·8) have active tuberculosis (45·3 times higher than the general population). There is substantial variation geographically and among females and males.

CONCLUSION: The substantial concentration of people with multiple risks and comorbidities requires improved strategies to screen, evaluate, treat and prevent these adverse consequences, which is crucial for global control efforts.